DETECTION PROCESS USING SURFACE-ENHANCED RAMAN SPECTROSCOPY () IN A MICRO-FLUIDIC FLOW SYSTEM EMPLOYING A SILVER SPOT AS SERS ENHANCING SUBSTRATE

摘要

The invention relates to a process for real-time detection of microorganisms, in particular bacteria, using surface-enhanced Raman spectroscopy (SERS), in a closed micro-fluidic system, employing, as a SERS enhancing substrate, a silver spot synthetized in situ under the action of laser radiation of a wavelength of 532 nm. According to the invention, the detection process comprises the following stages: 1. assembling the micro-fluidic cell made of a plexiglass board on the surface of which there is a system of engraved micro-fluidic channels with Y junction comprising two inlets and one outlet, each of the two inlets being connected by means of capillary tubes to a syringe with a solution of AgNOand Na citrate, and the outlet being connected to a hose for discharging the analytes and the biological sample, the plexiglass cell being tightly covered with a microscope slide and sealed by covering it with a metallic cover fixed with screws, 2. positioning the micro-fluidic cell onto the plate of a microscope and focusing the objective lens as to magnify 20 times, inside the micro-fluidic channel, in the exact place in which the formation of the Ag spot is desired, 3. setting the flowing parameters in the injection pump with syringes: flow rate of 0.25 ml/min, syringe diameter: 12.97 mm and delivered volume: 5 ml, 4. setting the laser power to 5 mW, 5. concomitantly starting the laser and the pump with syringes, when the micro-fluidic channel is filled with the two components, and, under the action of the laser, the Ag is reduced to Agand the Ag spot with SERS enhancing properties occurs, 6. injecting the bacteria test sample in order to prove the detection protocol and 7. recording SERS spectra and optimizing detection by determining the acquisition time and the laser power able to maintain viability of the biological test sample.